Fluorescent silicate glasses and methods for making same



Patented Apr. 20, 1948 ICATE GLASSES AND FLUORESCENT Sn. METHODS r R MAKING SAME Harrison P. Hood, Corning, N. Y., assignor to Corning Glass tion of New York No Drawing. Application Serial No. 540,7

Claims.

This invention relates to reduced glasses or glasses which are melted under reducing conditions through the use of reducing agents in their batches. Ordinary reducing agents such as carbon and carbonaceous materials are very efiective and, in glasses containing easily reducible materials such as cupric or cuprous oxides, and other glass-coloring elements or oxides, a very exact control of the amount of reducing agent is necessary in order to avoid overor under-reduction. Exact control is difiicult because many glasses are quite sensitive to small changes in amount of such reducing agents.

The primary object of this invention is to provide a new reducing agent theaction of which is milder and can be more easily controlled than that of prior reducing agents.

Another object is to provide a method of reduc ing glasses to a definite partial state of reduction.

Another object is to provide a method for partially or wholly reducing colored glasses.

Another object is to provide a method for reducing a glass containing a compound of copper or other glass coloring element to a definite partial state of reduction.

Another object is to increase the fluorescence of copper and other fiuorescing elements in glass.

Another object is to obtain the maximum flu crescent efiiciency from a glass containing copper as the sole fiuorescing material.

Another object is to improve the sensitivity and color contrast of photosensitive copper-containing glasses.

The elements or their oxides which are commonly employed to color glass such as vanadium, chromium, manganese, iron, copper, silver, gold,

Works, Corning, N.

uranium, and selenium are capable of producing various colorations depending upon the state of reduction of the glass. oxide may produce several effects in glass. In oxidized glasses, it produces a blue or blue-green color. When the glass is partially reduced, it becomes practically colorless. produces a red color. Copper-containing silicate glasses which are reduced to the colorless state fluoresce when the glass is irradiated with ultraviolet radiations. Certain colorless copper-containing glasses are also photosensitive, that is,

they are so afiected by wave lengths shorter than about 4000 Angstroms that subsequent heating causes coloration only of their irradiated portions. A mild or easily controlled reducing agent is For example, copper Further reduction amount of reducing agent have on the fluorescence than is the case when carbon Y., a corpora June 17, 1944, 93

2 oftentimes necessary and desirable for the reduction of colored glasses.

I have discovered that ammonium chloride acts as a mild reducing agent in glasses which contain small but substantial amounts of vanadium, chromium, manganese, iron, copper, silver, gold, uranium, or selenium, by means of whch the exact degree of reduction can be controlled more easily than has heretofore been possible. The amount of ammonium chloride required for a given reduction is many times the amount of carbon which is required for the same efiect. Among the many beneficial results flowing from my in vention I have found, for example, that when ammonium chloride is used as the sole reducing agent'in a copper-containing glass, the maximum fluorescence of the copper in the glass is more readily achieved and slight variations in the a smaller effect is employed as reducing agent. Best results are obtained when the copper content of the batch is equivalent to at least 0.1 0110 in the finished glass,

For example, two series of soda lime glasses were melted in which one series contained as re-' ducing agent varying amounts of carbon and the other series contained as reducing agent varying amounts of ammonium chloride, the batches being otherwise identical and containing each about 17% 0112012. The relative amounts of fluorescence produced by the various glasses as compared-to that produced by a standard calcium tungstate powder when irradiated by ultraviolet radiations were determined as follows:

The individual glasses were pulverized and their powders individually were irradiated by a low pressure mercury arc lamp. The resulting fluorescent light, if any, Was permitted to impinge on a photoelectric cell after passing through suitable filters to permit only selected wave lengths to strike the cell, which was shielded from all extraneous light. The electrical impulses thus generated by the photoelectric cell were registered by a galvanometer connected thereto. For calibrating the apparatus a strongly fluorescent material, such as'powdered calcium tungstate, was irradiated and the intensity of the irradiating light was adjusted by rheostat to give a convenient ga1- vanometer reading, in the present instance a reading of 40. The same intensity of irradiation was then employed for testing the powdered glass Fluorescent Reducing Agent alue Batch No.

.062% carbonsnhc Batch No. 2 contained an optimum contentiof carbon and batch No. 7 contained an optimum content of ammonium chloride, the fluorescence in each case being at almaximum. Batches 1, 5 and 6 contained an" insufiicient.,amountiofrrea ducing agent and were under reducemassshownaz by the fluorescence which is less thanimaximuni. Batches 4 and 8 on: the-rcontrary; were; overe reduced A and here-:alsos the 1 fluorescence'ris lessthan the maximum.

It will benoted that :in generalrtlieepercentage of carbon is smaller: than r' the" percentage: of? ammonium chloriderrequiredz fon:theesame..-efiect;z The percentage of,.carbon :isimore critical-ntharr: the percentage r of ammonium chloride: ands: slight changefrom the optimumicarbon content"! causes a; sudden:markeddepreciatiomim the zfluos rescencea- The same change :from sthei optimum-1 ammonium chloride?contentahasinmefiect om-the fluorescence. As a-.result:ofi'this-;.= a'rsmali :excess ordeficiencyin the ammonium chloridehaslittle 1 if any iefiect "and the stateof,:reductioni.is: there's: fore more: readily econtrolled; thanzl-whent carboni' is used asthe'reducin'g agent;

When: ammoniumzchlorider:isiemploye'dmsi :the-a reducing; agent: in: photosensitive -2 copper: corra tainingtglasses; theysare more' sensitiveatoxultra violet radiations and a greater degree of cone: trast is obtained in the tonal values ofitheaimage which sis developed: in: the: irradiatedzz-glass by'? heat: The :specifio zus'e ofaammonium TChIOIldiaSi a reducing. agent .il'i. such:photosensitivezglasses is-zdescribed fin patent applicationsaSer-iahNunr bers 513,414.41 and: 513,445s filedizon December 1943; by 2S2 DJ1stookeys'andiassigneditoithe lass: signee' of this: 4 applications The. :iollowingxbatches: intparts' bya-weight flareexamples of? compositions: containing copper-1 oxide and ammonium chloride in'-raccordanee with? my, invention:-

Table 1 a d 11001-1 1100 mm 12; 42 l 22."- 20 1 i.

Naqsir The above batches when-' meltedrwill produce i the following glasses as-calculated= in" percentfb? weight;

required. more NH4C1 than Table II Per cent Per cent Per cent Composition A is a glass having a high fluorescencewhen:irr'adiated with ultraviolet radiationsan'dis' suitable for the manufacture of enclosuresforifluorescent lamps. Composition B isiai tfansparenti photosensitive glass, and composition U is' a photosensitive glass which becomes opal on' being heated. Batches B and C batch A on account of the presence of the higher oxides of copper, tin and'cerium. Due to the presence of NH4C1 in the batch the copper in the resultant glass is believed 'tobe present as cuzo'; Howeveryin the analysis of a'glass 'containing copper -in' the'"cu-* prous-fdrm-no suitable analytical 'methodis avail able for its" direct determination as CuzO and it usually is' separated and weighed as metallitz copper? Bycalculati'on it may-"be expressed as either(Ji'izOforthe -equivalent amount or" C110. Accordingly the copper "content'bf the: glasses fof this "invention is stated in" equivalentamounts' or CuG" although-probably presentin" the glass as? CuzOJ The glass-*ofcomposition A .above has a copper content whichis equivalent to about 0.6 CuzO as shown in Table .II or'"0i66'%"CuOLIwl'iile the glassofcomposition'C"'has a copper content equivalent to about 0.11%? C1101" In ithefclaims; the copper contents "are therefore I expfes'se'diasthe equivalentv amounts orcuor Iri additlonjto the above examples}. other compositions, maybe employed. containing :one "or more ,i of f the? glass coloring el'e'nients vanadium, chromium, man-- ganese, liron copper silver,- .gold, uranium land selenium;

ltfhas not-.heretoore,. beenek'nown. thatiams monium chloride can act as v areducing-agent in: glass and in :f act -my.-researches show thatflordinarilytithas .nov such efiectL I have foundthat .7 it has areducing ,actioninthose glasses containing. a .compound .of one of the above named glasscoloring elements andiit',islgbellevedfth'at they, act as l catalysts inthepearli stages of, the melt to cause partial decompos'iti'onof the: ammonium radical to produce hydrogen. Other known glass. coloring elements producemo appreciable. color change non other desirable eflect when present, in the glassiwithl ammonium, chloride an'diarfe not jinclude'd-lwithin' the. scop of. the present invention l Practically any; glass composition is" suitable for use according to, myv invention. and,iwil1..'be, reduced by: ammonium chloride provided it con: tainsat least aismall "arn'ourit' ofl'the aforesaid glassacoldrihg elements, although .relatively large amounts mayibe present 'ifjdeslred." The-ammo mum; saltsiofani'oris having, an 'oxi dl'z'ingfeffctfi such 1 as the nitrate sulfate andi the I like," are ineffective f or I my; purpose. Preferably such an-'-' ions and" other "materialsfhaving an oxidizing" action, for example"; ,oxides'of polyyalenir ele"= suchasnrsenic; antimony," sulfur,'"etc:; shouldfpreferabiyf be absent because their-pres ence- *necess'it'at'es L'th'e fuse" of "'IargfeTamOuIItSf Qf ammonium chloride than would otherwise"- be necessary. If desired, the presence of excessive amounts of oxidizing materials may to some extent be compensated by the use of a small amount of carbon or equivalent reducing agent in addition to the ammonium chloride.

I claim:

1. A batch for afluorescent glass which consists of approximately 60% sand, 7% NazCOz, 23% K2CO3, 1% A1(OH)3, 8% CaCOs, 37% CuzClz, and .5% NH4C1.

2. The glass corresponding to the batch of claim 1.

3. The method of making a colorless fluorescent silicate glass which comprises introducing into a batch containing a copper compound equivalent to about 0.11% to 0.66% CuO in the finished glass, about .8 to 2.4 parts of ammonium chloride per 100 parts of SiOz, and melting the batch.

4. A batch for a colorless silicate glass which 20 contains a compound of copper equivalent to 0.11% to 0.66% CuO in the finished glass and .8 to 2.4 parts of ammonium chloride per 100 parts of SiOz.

6 5. The glass corresponding to the batch of claim 4.

HARRISON P. HOOD.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES Glass Industry, September 1935, page 273. 

